1. Field of the Invention
The present invention relates to a substrate processing apparatus for performing processing, such as washing, on substrates, such as silicon wafers, and to a substrate transporting device mounted to the substrate processing apparatus for transporting the substrates, such as silicon wafers, to a processing tank.
2. Description of the Related Art
In a substrate processing apparatus provided with a plurality of processing tanks and drying tanks containing various types of processing solutions (drug solution, rinsing solution) respectively, a substrate, such as a silicon wafer, is soaked into the processing solution in the processing tank by a substrate transporting device according to the processing flow. Provided on the upstream side of the substrate processing apparatus are a stocker for accommodating unprocessed substrates and transporting the same to the delivery position for delivering the same to the substrate transporting device mounted to the substrate processing apparatus and a substrate loading/unloading unit.
The stocker is a device for delivering the unprocessed substrates to the substrate processing apparatus, and transporting the processed substrates, which have passed through the substrate processing apparatus, to a subsequent process. Generally, the unprocessed substrates are delivered from the previous process in lots each including a plurality of substrates disposed in alignment in a cassette. Transporting means includes a cassette transporting system in which the substrates are transported together with the cassette, and so-called a cassette-less system in which only the substrates in the cassettes are held and transported. When constructing the apparatus, either one of these systems is selected as needed.
The substrate loading/unloading unit includes an unprocessed substrate loading unit for holding and taking all the substrates out from the cassette on the stocker delivered in the cassette transporting system and transporting them to the delivery position for delivering the substrates to the substrate transporting device of the substrate processing apparatus and a processed substrate unloading unit for receiving the processed substrates at the delivery position of the substrate transporting device, storing them into the cassette, and delivering them to the stocker.
FIG. 1 is a schematic drawing showing a construction of principal portion of a substrate processing apparatus 50 in the related art. As shown in FIG. 1, the substrate processing apparatus 50 includes a plurality of processing tanks 10-15 containing various types of processing solutions respectively, fastener washing tanks 8 and 9, a drying tank 20, an unprocessed substrate loading unit 35, a processed substrate unloading unit 36, substrate transporting devices R1, R2, and R3 moving along a transporting track 4. FIG. 1 also shows movable ranges of the substrate transporting devices R1, R2, and R3. The substrate transporting devices R1, R2, and R3 are constructed to move on the single track 4. The substrate transporting device R1 holds substrates delivered by the unprocessed substrate loading unit 35 and transports it while soaking it into the processing tanks 10, 11, 12, and 13 in sequence. The delivered substrates are subjected to processing, such as washing, in the processing tanks 10-13. The substrate transporting device R2 transports the substrates having processed in the processing tank 13 and soaks them into the processing tanks 14 and 15 located downstream thereof in sequence. The substrates having processed, for example, washed, in the processing tanks 14 and 15, are transported to the drying tank 20. The substrates having dried in the drying tank 20 are delivered to the processed substrate unloading unit 36 by the substrate transporting device R3. Delivery of the substrates between the substrate transporting devices R1 and R2 is carried out at the processing tank 13, and delivery of the substrates between the substrate transporting devices R2 and R3 is carried out at the drying tank 20. The processing tank at which delivery of the substrates between the substrate transporting devices is performed is referred to as transfer tank. The substrate transporting devices for transporting the substrates to the processing tanks other than the transfer tank are fixed. The substrate transporting devices R1, R2, and R3, shown in FIG. 1, are of cassette-less system.
Preparation of scheduling data for controlling the substrate transporting devices R1, R2, and R3 will now be described. The substrate transporting devices R1, R2, and R3 are controlled according to scheduling data prepared based on the recipe (control program), which includes control parameters such as processing time assigned for each processing tank. FIG. 2 is a flowchart for preparing a control sequence for the substrate processing apparatus by a scheduler in the related art. As shown in FIG. 2, data on the number of processing tanks to be installed, the processing time assigned for each processing tank, the type of processing solution, the movable range of the substrate transporting device, the transporting time, the processing conditions relating operating time of a lifter, and the transporting conditions, is entered through an input device such as a keyboard or by measurement of the transporting time or the operating time of the lifter (teaching) (Step S20). The computer then prepares a processing schedule based on entered data (Step S21). According to the prepared schedule, the computer calculates the time to start loading/unloading the substrates into/out of each processing tank based on data on the processing time and the type of processing solution in each processing tank. The computer also determines whether or not washing of the fastener of the substrate transporting device is necessary depending on the type of processing solution contained in the processing tank. Accordingly, the time to start and time to terminate processing for every processing tank, and the timing of loading and unloading of the substrates for each processing tank of the substrate transporting device are determined.
Then, whether or not the operation of the substrate transporting devices is required simultaneously at a plurality of processing tanks is determined from the timing of loading and unloading into/out of the substrate transporting device (Steps S22 and S23).
When the operation of the substrate transporting device is not required simultaneously at a plurality of processing tanks, the procedure goes to Step S25. When the operation of the substrate transporting device is required simultaneously at a plurality of processing tanks, the procedure goes to Step S24, in which the schedule is changed so that the timing of loading the substrates is delayed (Step S24), and then goes to Step S22. Then, when it is determined that the substrate transporting device can manage processing, the changed schedule is fixed (Step S25). Fixed schedule data is transferred to a control unit of the substrate processing apparatus 1 (Step S26), and then the substrate processing apparatus 1 starts processing (Step S27). With the steps described above, the substrates in the unprocessed substrate loading unit 35 are transported to a first processing tank by a substrate transporting device RT1, and processing of those substrates is started. (See Japanese Examined Patent Application Publication No. 7-22144, Japanese Unexamined Patent Application Publication No. 10-172939, Japanese Unexamined Patent Application Publication No. 2002-172367)
As described above, since the processing time is predetermined by scheduling data for each processing tank, it is necessary to take the substrates out from the processing tank immediately after the processing time assigned for each processing tank has elapsed and to transport it to the next processing tank. However, according to the substrate transporting device in the related art, the movable range of the substrate transporting device across the plurality of tanks is fixed. Therefore, when the substrate transporting device is transporting one lot of substrates in the movable range, and if transportation of another lot of substrates in another processing tank is required in the movable range, the substrate transporting device in operation cannot access to another processing tank. Therefore, another lot of substrates in another processing tank has to wait until the current operation of the substrate transporting device is terminated.
FIG. 3 is a timing chart showing processing of substrates in each processing tank in chronological order. Arrows shown in FIG. 3 represent the substrate transporting operations to be performed by the substrate transporting device, and hutched bars represent that processing is in progress in the processing tank, and the length of the hutched bar represents the processing time.
As shown in FIG. 3, when groups of substrates (a first lot, a second lot, and a third lot shown by circles) shown in FIG. 3 are loaded in sequence starting from the first processing tank 10 from the unprocessed substrate loading unit 35, since the processing time is limited for each processing tank, two processing tanks require transportation of the substrates simultaneously at the timings t1 and t2, as shown in FIG. 3, namely, when transferred from the processing tank 10 to the processing tank 11, and from the processing tank 12 to the processing tank 13. Since only one substrate transporting device is available in the range from the processing tank 10 to the processing tank 13, one processing tank has to wait until transportation at another processing tank is terminated.
In order to solve such a problem, it is necessary to delay loading of the substrates into the first processing tank so that completion of processing of the substrates does not occur at a plurality of tanks simultaneously. In the conventional system, as shown in FIG. 4, loading of the groups of substrates (first lot, second lot) into the first processing tank is delayed, so that completion of processing of the substrates does not occur at a plurality of tanks simultaneously.
However, by delaying loading of the substrates into the processing tank, a throughput of the substrate in the substrate processing apparatus 50 is restrained, and thus the number of substrates that can be processed during a predetermined time period is reduced. Therefore, improvement of the throughput of substrate processing in the substrate processing apparatus 50 is a subject to be achieved.